1. Technical Field of the Invention
The present invention relates to cellular telephone networks and, in particular, to the reverse communication of mobile station calling service (data calling) capabilities and the intelligent paging of a mobile station in connection with the termination of an incoming data call.
2. Description of Related Art
Operation of a cellular telephone network to handle an incoming call dialed to a cellular subscriber mobile station is well known. Responsive to receipt at an originating (or gateway) switching node of the incoming call dialed to a mobile station, a location request (send routing) message is sent to the home location register for the dialed mobile station. The home location register then identifies a switching node currently serving the dialed mobile station. A routing request (provide roaming) message is then sent from the home location register to the serving (or visited) switching node to prepare for delivery of the call. The serving switching node then pages for the mobile station within the network. Responsive to a paging acknowledgment, the mobile station is located and the serving switching node assigns an appropriate routing number (for example, a temporary location directory number or a roaming number) for that location. The routing number is then delivered back to the originating switching node via the home location register where it is used to forward the incoming call over a trunk call connection established between the originating switching node and the serving switching node. Delivery of the incoming call to the mobile station from the serving switching node is then accomplished by establishing a connection with a base station currently serving the mobile station. A radio frequency communications link is then established between the base station and the mobile station to carry the connection, and it is over this radio frequency communications link that the incoming call delivery is handled.
Cellular telephone networks utilize a control channel to broadcast control signals within each of the included plurality of cells. In connection with the locating of a mobile station, a paging signal is transmitted over the control channel for certain ones of the cells. In order to provide the greatest likelihood of establishing location, the paging signal must be transmitted within every cell covering the service area of the network. The capacity of the control channel, however, is limited because its data transmission rate is relatively slow and it is used by the network to transmit many control related messages other than paging signals. Paging in every cell is then not an acceptable option as this would adversely affect control channel capacity, and would preclude network paging for multiple mobile stations in a simultaneous manner. Procedures have accordingly been established to utilize the limited capacity of the control channel as efficiently as possible, while at the same time ensuring an acceptable success rate for paging to facilitate call delivery.
One paging procedure that has been successfully utilized is to define a plurality of location areas (LA's) within the service area (SA) of the cellular telephone network. Each location area typically includes a plurality of individual cells. As mobile stations move about the service area, they register with the network each time they enter into a new location area. A record of this registration is kept, and selective paging is performed in each of the cells of the location area where the called mobile station last registered. If the paging signal is not acknowledged by the mobile station, the network next pages in a paging area (PA) which is larger than the location area in which the mobile station last registered, but smaller than the service area. Paging over the entire service area (i.e., global) for a mobile station is performed last, and is preferably implemented only in emergency situations.
Many different kinds of calling services are now being offered by cellular service providers. Conventionally, of course, the calling service of primary use and importance to subscribers has been voice calling. With increased sophistication in the network, and increased demands of subscribers for service variety, other calling services, such as data calling, are now available for subscriber use. Older mobile stations, however, have limited calling service capability such that they can, for example, only make and receive voice calls. With these new calling services being supported by the network, an incoming call implicating a calling service other than voice calling may be directed towards a mobile station that is incapable of providing support to that implicated calling service. In such cases, it would be a waste of limited network communications resources to page for that mobile station in connection with the incoming call.
To address this problem, EIA/TIA Interim Standard IS-136.1 provides a message (i.e., the "Capability Report" message) for mobile station transmission on the random access channel (RACH) of the reverse digital control channel (DCC) at the time of mobile station registration. See, IS-136.1 .sctn.6.4.4.5 (12/94). In the DCC Capability Report message, the mobile station supplies the network with information concerning, among other things, its capabilities with respect to supporting calling services such as data services. For data services in particular, using the DCC Capability Report message, the mobile station may identify whether it supports, for example, asynchronous data communication, G3Fax communication, half rate DTC communication, double rate DTC communication, triple rate DTC communication, STU-III, or asymmetrical bandwidth communication. Once the network has knowledge of the supported calling services information, intelligent paging decisions may be made in response to an incoming call implicating one of those services. The network, operating within the context of a conventional call delivery scenario, then evaluates the information provided by a given mobile station in its DCC Capability Report message, and if the mobile station does not provide support for a calling service implicated by an incoming call, no paging is performed and a mobile station not available message is returned to the originating switching node.
When a mobile station is currently being served by a cell having only an analog control channel (ACC) capability, no transport mechanism exists for communicating the mobile station IS-136.1 DCC Capability Report message information concerning supported calling services such as data services. As another concern, the information stored by the network in the subscriber record following receipt of a DCC Capability Report message may subsequently become lost if the subscriber record is recycled. In these situations, the network may not know which calling services are supported by a served mobile station at the time of call delivery. Absent network knowledge of such information, instances may arise where inefficient and unnecessary paging occurs with respect to that mobile station in response to an incoming call implicating a non-supported calling service. What is needed then is a technique, other than through (and preferably in addition to) the use of the IS-136.1 DCC Capability Report message, for a mobile station to provide the network with information on mobile station supported calling services.